Sergio Aguero has backed Manchester City to successfully defend their Premier League title after the disappointment of Champions League elimination on Wednesday.

City were left to fight for a place in this season's Europa League after succumbing to a 1-1 draw with Real Madrid, raising doubts over their current form and forcing Roberto Mancini to defend his position at the club.

The English champions were criticised for failing to hit their stride in the opening rounds of the Premier League season, but a convincing 5-0 win over Aston Villa last weekend restored their title credentials.

Aguero admits that City's Premier League rivals may have recruited better over the summer, but that only motivates his side to pursue back-to-back championships.

"I'm sure we will retain our title," Aguero said. "It's true that Chelsea, Manchester United, Arsenal and other teams have strengthened their squads intelligently compared with last season.

"But we are the champions and they want to take us on - so that's only to be expected. It won't be easy for them because we are growing as a team and we get to know each other better every time we play.

"It's true that we don't have the same flair in games that we had last season and we've scored fewer goals for sure. But the Premier League table says something different. It says we are very hard to beat, top of the table and defending well, so we can't be doing that badly can we?"

Aguero believes a number of injury setbacks has made it difficult for City to gather momentum, with Vincent Kompany a chance of missing the showdown with Chelsea on Sunday after suffering a knee injury against Real.

"We have been hindered by a string of injuries to important players - David Silva, [Pablo] Zabaleta, [Javi] Garcia, [Joleon] Lescott, [Micah] Richards, Maicon, [Gareth] Barry, [Samir] Nasri, [James] Milner, myself - it's not easy when they all happen simultaneously," he said. "Last season we had very few injuries.

"If we have been succeeding despite these difficulties, then it makes me believe that the best is still to come and we'll be able to repeat our form of last year. We are destined to win more trophies and, barring any major setbacks, we will.

"When I first arrived at City after my first game against Swansea, I said I hoped this was the beginning of something very big. Our Premier League title showed it possibly was and that we had great things ahead. As I said, I firmly believe the best is yet to come."

Aguero has scored five goals in six starts for City this Premier League campaign and after an injury blow early on, the Argentinian feels he is returning to form.

"From a personal point of view it was a pity to get injured so early in the new season," he said. "I'd had an intense pre-season and felt in terrific shape.

"Then I had to stop and start back from scratch, which was hardly ideal. But I'm in top form right now and feel sharp and hungry. Injuries in general can be frustrating because they can halt you in full flow. But in my case I was so motivated to get back on the field that it overcame any frustration."